Proposal for transparent cascading of 3:4 up and subsequent 4:3 down conversion filtering

A proposal is described which is based on a 3:4 FIR Nyquist up conversion filter and a corresponding 4:3 FIR Nyquist down conversion filter that on cascading result mathematically in the identity operator. The proposed filters are applied horizontally to critical video signals. Experimental results show that, despite the limited numerical precision of the filter coefficients and filter calculations, an almost (55 dB) transparent cascade can be achieved. The small amplitude errors are in the order of ±1 unit and found to be invisible when the pictures are displayed on a grade 1 studio monitor of standard TV resolution. Additionally, a high subjective quality for up converted pictures is achieved and maintained over several cascades